The present invention relates to a failsafe sensing edge for use with automatic doors and gates.
The use of safety devices on automatically operating doors and gates is well known. In a usual such arrangement, for example, the door will automatically retract when an object interferes with its closing. The accepted meaning of "failsafe" in the industry is self-monitoring.
Typical designs for accomplishing this result include the use of lights with photoelectric detectors and switches which close on contact with the interfering object.
The drawbacks of arrangements currently in use include problems caused by the presence of dust, dirt, and ambient lighting in photoelectric systems, and problems with humidity and moisture in the case of switches mounted in sealed electrical door edges.
A variety of United States Patents have issued which disclose such safety devices.
U.S. Pat. No. 2,791,654 discloses a combined safe edge and sight guard for elevator doors using a micro switch which is closed when a cushioned edge is depressed by an interfering object.
U.S. Pat. No. 3,001,038 shows an overhead closure safety halting system utilizing an actuating bar mounted on the leading edge of the garage door to close a switch when interference occurs.
U.S. Pat. No. 3,003,303 illustrates a pneumatic safety edge for power operated doors designed to avoid the use of electrical switches. In this design, pneumatic tubes in the leading edge of the door are compressed upon making contact with an object with a consequent increase in pressure which is transferred to a sensor located away from the door to energize the safety system.
U.S. Pat. No. 3,462,885 discloses a safety edge for a door which employs a pair of electrical conductors mounted in a compressible door edge to make contact upon the edge being compressed by an object.
U.S. Pat. No. 4,115,952 shows a safety door edge which employs a flexible channel along the door edge containing a pair of contacts which come together when the channel is compressed.
U.S. Pat. No. 4,452,009 uses a light barrier and light receivers and sender. In this arrangement, the light exit locations are cleaned each time the door is used.
U.S. Pat. No. 4,773,183 shows a contact sensitive apparatus for a power window or sun roof in which a sealed tube is employed containing a fluid which communicates with a controller to sense an interfering object.
U.S. Pat. No. 4,944,116 describes a sensor strip which acts as a light guide for a light emitter and sensor. When the strip is distorted it interferes with light transmission.
U.S. Pat. No. 4,953,608 discloses a safety device for roll-up doors relying on photoelectric cells.
None of the aforementioned patents teaches or suggests the present invention.